Translocations between the long arms of chromosomes 1 and 5 in hematologic malignancies are strongly associated with neoplasms of the myeloid lineages.

The clinical, morphologic, and cytogenetic features of two hematologic malignancies--one acute myeloid leukemia with minimal differentiation (AML-MO) and one therapy-related myelodysplastic syndrome (MDS)--with unbalanced translocations between 1q and 5q are reported. The translocations resulted in loss of 5q material in both cases and gain of 1q in the MDS. A compilation of previously published hematologic malignancies with translocations involving the long arms of chromosomes 1 and 5 revealed a total of 23 cases--11 with unbalanced and 12 with balanced t(1;5)--with the following morphologies: 11 AML, three MDS, two Philadelphia-positive chronic myeloid leukemias, three chronic myeloproliferative disorders, three acute lymphoblastic leukemias, and one chronic lymphocytic leukemia. Four patients had received chemotherapy including alkylating agents for a previous malignancy and one had been exposed to thorotrast. Among the 14 patients for whom survival data exist, all except three have died. The t(1;5) was found as the sole abnormality in six cases, whereas it was apparently secondary--occurring in a subclone or together with the well-known primary abnormalities t(8;21), t(9;22), and t(15;17)--in nine cases. The breakpoints in 1q varied from 1q11 to 1q43, with a clustering to 1q21-23, and the 5q breaks occurred in 5q11 to 5q35, mainly in the distal 5q3 region. The unbalanced 1;5 translocations resulted in gain of 1q material in eight of the 11 cases, 1q21-1qter being duplicated in four of them, and in loss of 5q, most often the 5q3 region, in 10 of the neoplasms. We conclude that translocations between 1q and 5q, although cytogenetically heterogeneous, are associated with hematologic malignancies of the myeloid lineages and with previous mutagenic exposure, and that t(1;5) seems to confer a poor prognosis.